1. Technical Field
The following description relates to one or more FTP communication systems with a network storage device connected to a host device such as a personal computer and workstation.
2. Related Art
Recently, there is widely known as an example of a recording medium a so-called memory card configured with a non-volatile memory, such as a flash memory, being packaged in a card form. The memory card is rapidly spreading as a data recording medium usable for a digital device such as a digital camera and portable music player. A format of the memory card is not unified, and there come in a market various formats of memory cards, such as CompactFlash (trademark registered, hereinafter, simply referred to as “CF”), SmartMedia (trademark registered, hereinafter, simply referred to as “SM”), Memory Stick (trademark registered, hereinafter, simply referred to as “MS”), and SD Memory Card (trademark registered, hereinafter, simply referred to as “SD”).
It is possible to access data stored on the aforementioned memory card from a personal computer (PC) using a memory card reader/writer (an example of a network storage device, hereinafter, simply referred to as “reader/writer”) which is configured to read data from the memory card and write data into the memory card in a state connected with the PC. Thereby, data communication between the PC and memory card becomes possible (for example, see Japanese Patent Provisional Publications No. 2005-18645 and No. 2005-107875). In these years, a printer with such a reader/writer incorporated therein has come to be widely used. Thereby, an image can directly be printed with the memory card storing thereon a JPEG format file of the image being inserted in the reader/writer without using the PC.
The aforementioned printer can be configured as a network printer connectable with a plurality of PCs via a network so as to be commonly used by the plurality of PCs. In this case, the network printer and the PCs are generally interconnected via a TCP/IP (Transmission Control Protocol/Internet Protocol) network (e.g., Local Area Network). Further, when the memory card, which is to be used for storing thereon an image data file taken by the digital camera or the mobile phone with the digital camera, is inserted in the reader/writer of the network printer, the network printer with an FTP (File Transfer Protocol) server program installed therein can transfer the image data file to the PCs based on the FTP. Namely, the reader/writer of the printer is usable as an external network storage device of the PC.
However, when there is performed the FTP-based data communication between the PC and the aforementioned network reader/writer (or the printer with the reader/writer) provided with an FTP server function, attribute information of the data file might be changed into information different from original one stored in a transfer source. For instance, after the data file with an attribute thereof originally set to be “READ ONLY” is transferred from the PC and stored into the reader/writer (or, transferred from the reader/writer and stored into the PC), the attribute might be changed into one which represents that both “READ/WRITE” operations are possible.
Further, date information (or date and time information) stored as a part of the attribute information that represents a creation date (or update date) of the data file might be changed into date information that represents date when the data file has been transferred (especially in the case of file transfer from the PC to the reader/writer). It is a serious problem that the attribute information and/or date information are lost as described above in the case of a data file with important attribute information and/or date information included therein, such as a data file with attribute information intentionally set to be “READ ONLY” to prevent careless data rewriting, a time series data file with information representing a state of frequently updated data at each update time, and an image data file with information representing a date when the image data file was taken by a digital camera.
The aforementioned problem is caused for a following reason. Since the FTP, which is an old protocol in a communication protocol history, is designed based on an assumption that an FTP server is provided with a UNIX-based file system (UNIX: trademark registered), commands of the file system for acquiring and updating the attribute information of the data file do not comply with a file attribute format for a file system provided to the PC with Windows (trademark registered) installed as an OS (Operating System) therein.